The invention relates to an image display device comprising a light source, a separating means for splitting a light beam from the light source into light beams having at least three different colors, at least three light modulation panels, guide means for guiding each light beam towards an associated light modulation panel, combination means for combining the light beams modulated by the light modulation panels, and at least one adjusting mechanism for adjusting at least one light modulation panel with respect to the combination means.
The invention also relates to an adjusting mechanism.
Such an image display device is, for example, a projection television in which light beams modulated by the light modulation panels are imaged on a projection screen after they have been combined by the combination means such as, for example, a prism. It will be evident that the light beams from the different light modulation panels should be combined in a correct manner so as to obtain a satisfactory image. To this end, the light modulation panels should be accurately adjusted with respect to one another and with respect to the combination means.
In an image display device known from U.S. Pat. No. 5,868,485, a first fixation plate is connected to the prism while a second fixation plate is connected to the light modulation panel. The fixation plates are adjusted with respect to each other by means of wedges to be arranged between the plates. After these wedges have been positioned, they are connected to the fixation plates and a definitive connection between the two fixation plates is obtained.
A drawback of such an adjusting mechanism is that all of the six degrees of freedom of the light modulation panel with respect to the combination means must be determined by means of the wedges. A further drawback of the use of such wedges is that, due to the displacement of a wedge, the light modulation panel is displaced and tilted in different directions and at different angles with respect to the prism. This relatively complicates the adjustment of the light modulation panel with respect to the prism. Moreover, the adjusting mechanism comprises a relatively large number of components so that its assembly is relatively complicated.
It is an object of the invention to provide an image display device in which a light modulation panel can be adjusted with respect to the combination means in a simple manner.
In the image display device according to the invention, this object is achieved in that the adjusting mechanism is provided with two plates extending transversely to the light modulation panel, the first plate having at least two points of fixation, each of which is movable in the plane of the plate by means of a parallelogram mechanism, and the second plate having at least one point of fixation which is movable in the plane of the second plate by means of a parallelogram mechanism, each parallelogram mechanism being provided with an associated locking mechanism, the adjusting mechanism being further provided with a bearing plate connected to the points of fixation and supporting the light modulation panel, which bearing plate is movable by means of the three parallelogram mechanisms in a direction extending transversely to the bearing plate and is tiltable about axes extending in the plane of the bearing plate.
By moving each point of fixation through the same distance by means of the associated parallelogram mechanism, a displacement of the bearing plate in a direction extending transversely to the bearing plate is obtained. If the points of fixation of the first plate are moved in a direction remote from the combination means while the point of fixation of the second plate is moved towards the combination means, a tilt about an axis extending parallel between the plates will take place. By moving the two points of fixation of the first plate in different directions, a tilt of the bearing plate about an axis of the bearing plate extending transversely to the plate will take place. Thus, any desired displacement or tilt of the bearing plate in said three degrees of freedom is possible in a simple manner. By adjusting the bearing plate with respect to the combination means in this manner, the bearing plate can be arranged, for example, in the focal plane of the combination means.
If the line modulation panel only needs to be arranged in one plane, such an adjusting mechanism will be sufficient.
An embodiment of the image display device according to the invention is characterized in that each parallelogram mechanism is formed by four leaf hinges in the plate.
A parallelogram mechanism can be easily provided in a plate by means of leaf hinges.
A further embodiment of the image display device according to the invention is characterized in that the adjusting mechanism is provided with a supporting plate which extends parallel to the bearing plate and to which the light modulation panel is connected, said supporting plate being movable with respect to the bearing plate in directions extending parallel to the bearing plate, and being tiltable about an axis extending transversely to the bearing plate.
After the bearing plate has been arranged in a plane, for example, the focal plane, the light modulation panel can be given any desired orientation in the plane by means of the supporting plate and by adjustment in the other three degrees of freedom.
By using the supporting plate, a clear separation is obtained between arranging the light modulation panel in the plane and subsequently positioning the light modulation panel in a desired orientation in the plane.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.